1. Field of the Invention
The present invention relates to the alkylation of salicylic acid with long-chain olefins. These alkylated salicylic acids can be overbased to form useful lubricating oil additives.
2. Description of Related Art
It is known to use alkaline earth metal salts of organic carboxylic acids as additives for lubricating oil compositions. These salts have a dispersant property that helps ensure that the insides of engine cylinders remain clean and that deposition of carbonaceous products on pistons and in piston grooves is counteracted, thus preventing piston-ring sticking.
It is also known to prepare basic (or overbased) alkaline earth metal salts of such acids. The overbasing provides an alkaline reserve which, when applied in lubricating oil compositions, reacts with and neutralizes acidic compounds formed during the operation of the engine in which the composition is applied. Hence, any sludge that may arise is dispersed owing to the dispersant property of the salt, while acids that would enhance sludge formation are neutralized.
Overbased salicylates are prepared by overbasing the corresponding alkylated salicylic acids. The alkyl group is typically a long chain alkyl group of greater than about 14 carbon atoms so as to impart oil solubility. Alkylated salicylic acids are conventionally prepared by the alkylation of a phenol to form an alkylphenol followed by carboxylation of the alkylphenol by the Kolbe-Schmitt reaction to provide the alkylated salicyclic acid. In addition to the adverse economics attributable to the use of high temperatures and/or pressures, the Kolbe-Schmitt route to alkylated salicylic acids suffers from the problem that, when substantially linear alkylation feeds are employed, not all of the long-chain alkylphenol is readily carboxylated. Specifically, conventional alkylation of phenol with a substantially linear alkylation feed provides for approximately a 50:50 mixture of ortho-alkylphenol and para-alkylphenol. While the Kolbe-Schmitt reaction readily carboxylates the resulting long chain para-alkylphenol, the resulting long chain ortho-alkylphenol is less reactive and only about 70 percent of total amount of the alkylphenol derived from a substantially linear alkylation feed is typically converted to alkylated salicylic acid during this reaction.
One method of circumventing this problem is to alkylate an alkyl salicylate (e.g., methyl salicylate) and then subject the resulting alkylated alkyl salicylate to hydrolysis so as to provide for the alkylated salicylic acid. Methods of alkylating alkyl salicylates are disclosed in U.S. Pat. No. 5,434,293.
DD-A-269 619 and DD-A-293 108 both disclose the direct alkylation of salicylic acid with an olefin using an acidic ion exchange resin or polyphosphoric acid respectively as catalyst. Both documents teach that the use of sulfuric acid as a catalyst (in prior art processes not involving alkylation of the acid with an olefin) is undesirable because it has many disadvantages, such as corrosion problems and side reactions.
DE 689 600 discloses the use of perchloric acid as the catalyst.
U.S. Pat. No. 1,998,750 discloses the condensation of salicylic acid with any nonaromatic monohydric alcohol having from 5 to 7 carbon atoms, or with compounds capable of furnishing an amyl-, hexyl-, cyclohexyl-, or heptyl- group, in the presence of sulfuric acid.
U.S. Pat. No. 4,810,398 discloses a basic alkaline earth metal salt of a blend of organic carboxylic acids is prepared by (a) preparing a mixture of one equivalent of the blend of organic carboxylic acids and more than one equivalent of an alkaline earth metal hydroxide and/or oxide in a hydrocarbon solvent; (b) introducing carbon dioxide into the mixture obtained in an amount of at least 0.5 equivalent carbon dioxide per equivalent of excess alkaline earth metal; and (c) removing residual solids, if any, and an aqueous layer, if any, whereby the blend of organic carboxylic acids comprises a C8-30 alkyl salicylic acid and one or more alkanecarboxylic acids in which the alkyl moiety is branched and has from 4 to 40 carbon atoms. Such a salt has dispersant properties and is said to be suitable for use in lubricating oil and fuel compositions.
U.S. Pat. No. 4,869,837 discloses a process for the preparation of a basic alkaline earth metal salt of a blend of organic carboxylic acids, which comprises (a) preparing a mixture of one equivalent of the blend of organic carboxylic acids and more than one equivalent of an alkaline earth metal hydroxide and/or oxide in a hydrocarbon solvent; (b) introducing carbon dioxide into the mixture obtained in an amount of at least 0.5 equivalent carbon dioxide per equivalent of excess alkaline earth metal; and (c) removing residual solids, if any, and an aqueous layer, if any, whereby the blend of organic carboxylic acids comprises an oil-soluble alkyl salicylic acid and one or more hydrocarbon substituted succinic acids or anhydrides, in which the hydrocarbon radical has a number average molecular weight from 120 to 5000.
U.S. Pat. No. 4,876,020 discloses a lubricating oil composition comprising a lubricating base oil, one or more overbased alkaline earth metal salts of an aromatic carboxylic acid, and a stabilizing agent which has been selected from a polyalkoxylated alcohol having a molecular weight from 150 to 1500.
U.S. Pat. No. 5,049,685 discloses a nuclear substituted salicylic acid represented by the following general formula
wherein R1 represents a methyl group, an isopropyl group, a tert-butyl group, a tert-amyl group, a tert-hexyl group, a tert-octyl group, an α,α-dialkylbenzyl group or a nuclear substituted α,α-dialkylbenzyl group; and R2 represents a tert-butyl group, a tert-amyl group, a tert-hexyl group, a tert-octyl group, an α,α-dialkylbenzyl group or a nuclear substituted α,α-dialkylbenzyl group) and a salt thereof. The nuclear substituted salicylic acids and salts thereof are said to have good solubility in water, organic solvents or organic polymeric compounds and that they are very favorable as bactericidal and germicidal agents, stabilizers for polymeric compounds or color developing agents for recording materials.
U.S. Pat. No. 5,415,792 discloses overbased alkyl alkyl salicylates that are said to be useful additives for lubricating oil compositions. In particular, the compositions impart detergency and dispersancy to the lubricating oil composition as well as provide for an alkalinity reserve.
U.S. Pat. No. 5,434,293 discloses a method for alkylating alkyl salicylates using a solid acidic alkylation catalyst and approximately equimolar amounts of alkyl salicylate and alkylating feedstock.
U.S. Pat. No. 5,451,331 discloses a process for the production of a lubricating oil additive concentrate having a TBN greater than 300 that comprises reacting, at elevated temperature, component (A) a defined salicylic acid derivative, component (B) an alkaline earth metal base added either in a single addition or in a plurality of additions at intermediate points during the reaction, component (C) at least one compound which is (i) water, (ii) a polyhydric alcohol having 2 to 4 carbon atoms, (iii) a di-(C3 or C4) glycol, (iv) a tri-(C2–C4) glycol, (iv) a mono- or poly-alkylene glycol alkyl ether of the formula (I) R(OR1)x OR2 (I) wherein R is a C1 to C6 alkyl group, R1 is an alkylene group R2 is hydrogen or a C1 to C6 alkyl group and x is an integer from 1 to 6, (vi) a C1 to C20 monohydric alcohol, (vii) a C1 to C20 ketone, (viii) a C1 to C10 carboxylic acid ester, or (ix) a C1 to C20 ether, component (D) a lubricating oil, component (E) carbon dioxide added subsequent to the, or each, addition of component (B), component (F) a defined carboxylic acid or derivative, and component (G) at least one compound which is (i) an inorganic halide of (ii) an ammonium alkanoate or mono-, di-, tri- or tetra-alkyl ammonium formate or alkanoate provided that, when component (G) is (ii), component (F) is not an acid chloride, the weight ratios of all components being such as to produce a concentrate having a TBN greater than 300.
U.S. Pat. No. 5,734,078 discloses a process for the production of an alkyl salicylic acid in which the alkyl substituent has at least 6 carbon atoms, comprising reacting salicylic acid with an olefin having at least 6 carbon atoms at elevated temperature in the presence of sulfuric acid as a catalyst. Lubricating oil additives comprising a metal salt of such alkylated salicylic acids and a process for making them are also disclosed.
U.S. Pat. No. 5,792,735 discloses a lubricating oil composition said to be suitable for use in low or medium speed diesel engines that comprises a fuel oil with a residual oil content characterized in that the lubricating oil composition further comprises a hydrocarbyl-substituted phenate concentrate having a TBN greater than 300, and at least one of a hydrocarbyl-substituted salicylate and a hydrocarbyl-substitute sulphonate. The hydrocarbyl-substituted phenate is preferably one modified by incorporation of a carboxylic acid of the formula RCH(R1)CO2H where R is a C10–C24 alkyl group and R1 is hydrogen or a C1 to C4 alkyl group, e.g., stearic acid.
U.S. Pat. No. 6,034,039 discloses complex detergents that are said to provide improved deposit control and corrosion protection in crankcase lubricants.
The disclosures of the foregoing are incorporated herein by reference in their entirety.